Polyolefins are non-polar products which typically have a poor affinity with traditional materials such as, for example, glass and metals in general, and are incompatible with polar synthetic polymers such as polyesters and polyamides. The ability to functionalize and therefore modify these typically chemically inert polyolefins has been highly sought after. Furthermore, the ability to efficiently and reproducibly functionalize materials such as polyethylene, polypropylene, and related copolymers with a reactive group that could be further utilized in numerous processes and end uses is particularly desirable.
Various methods to functionalize polyolefins are known. However, such methods are often characterized as tedious, time consuming, typically require air/moisture sensitive chemicals and are generally not efficient.
Examples of processes to functionalize polyolefins include the use of free radical chemistry in the reactor, such as in high pressure reactors to create ethylene-vinyl acetate type copolymers. These processes often do not provide adequate control over the number of functional groups added to the polymer.
Examples of processes to functionalize polyolefins post polymerization include grafting, wherein the polyolefin is contacted with maleic anhydride or a similar grafting material, typically in an extruder. Such processes are difficult to control and tend to cross-link or chain scission the polymer, thereby changing the properties of the functionalized polymer. Functionalization in solution is also possible, but this process is also difficult to control and requires the identification of common solvents for the polyolefins, the functional groups, and the catalysts. Additionally, solution functionalization can be ineffective with many side reactions. Functionalization in solution also requires an extra step of solvent removal.
Antiwear and Extreme Pressure Additives:
Internal combustion engine lubricating oils require the presence of antiwear and/or extreme pressure (EP) additives in order to provide adequate antiwear protection for the engine. Increasingly specifications for engine oil performance have exhibited a trend for improved antiwear properties of the oil. More specifically, fuel economy improvement strongly depends on the reduction of lubricant viscosity. This leads the engine parts run under more severe conditions causing increasing engine wear. To enable enhanced durability for the low viscosity fuel economy oils, there is a need to develop improved antiwear technologies.
While there are many different types of antiwear additives, for several decades the principal antiwear additive for internal combustion engine crankcase oils is a metal alkylthiophosphate and more particularly a metal dialkyldithiophosphate in which the primary metal constituent is zinc, or zinc dialkyldithiophosphate (ZDDP). ZDDP compounds generally are of the formula Zn[SP(S)(OR1)(OR2)]2 where R1 and R2 are C1-C18 alkyl groups, preferably C2-C12 alkyl groups. These alkyl groups may be straight chain or branched. The ZDDP is typically used in amounts of from about 0.4 to 1.4 wt % of the total lube oil composition, although more or less can often be used advantageously.
ZDDP provides excellent wear protection under mild wear conditions. However, when the viscosity of the base fluid is significantly low, i.e. when the contact severity is too high, ZDDP often fails to perform. Another negative aspect of ZDDP is that it generates volatile phosphorous when decomposed. In addition, phosphorous in the decomposed and volatile ZDDP products are responsible for poisoning the catalyst of the catalytic converter and damaging the oxygen sensors of vehicle exhaust systems. There is also increasing pressure from OEMs and government agencies to reduce P level (ZDDP) in the current engine oils. However, lowering P level may pose an enormous risk to the engine durability. Hence, there is a need for new and improved ashless antiwear additives for engine oils that do not have any harmful phosphorous and thus do not degrade the engine emission system and at the same time provides extended wear protection to engines, especially when the fuel economic low viscosity lubricants are used.
A variety of non-phosphorous additives are also used as antiwear additives. Sulfurized olefins are useful as antiwear and EP additives. Sulfur-containing olefins can be prepared by sulfurization or various organic materials including aliphatic, arylaliphatic or alicyclic olefinic hydrocarbons containing from about 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms. The olefinic compounds contain at least one non-aromatic double bond. Such compounds are defined by the formulaR3R4C═CR5R6 where each of R3-R6 are independently hydrogen or a hydrocarbon radical. Preferred hydrocarbon radicals are alkyl or alkenyl radicals. Any two of R3-R6 may be connected so as to form a cyclic ring. Additional information concerning sulfurized olefins and their preparation can be found in U.S. Pat. No. 4,941,984.
The use of polysulfides of thiophosphorus acids and thiophosphorus acid esters as lubricant additives is disclosed in U.S. Pat. Nos. 2,443,264; 2,471,115; 2,526,497; and 2,591,577. Addition of phosphorothionyl disulfides as an antiwear, antioxidant, and EP additive is disclosed in U.S. Pat. No. 3,770,854. Use of alkylthiocarbamoyl compounds (bis(dibutyl)thiocarbamoyl, for example) in combination with a molybdenum compound (oxymolybdenum diisopropylphosphorodithioate sulfide, for example) and a phosphorous ester (dibutyl hydrogen phosphite, for example) as antiwear additives in lubricants is disclosed in U.S. Pat. No. 4,501,678. U.S. Pat. No. 4,758,362 discloses use of a carbamate additive to provide improved antiwear and extreme pressure properties. The use of thiocarbamate as an antiwear additive is disclosed in U.S. Pat. No. 5,693,598. Thiocarbamate/molybdenum complexes such as moly-sulfur alkyl dithiocarbamate trimer complex (R═C8-C18 alkyl) are also useful antiwear agents. The use or addition of such materials should be kept to a minimum if the object is to produce low SAP formulations. Each of the aforementioned patents is incorporated by reference herein in its entirety.
Esters of glycerol may be used as antiwear agents. For example, mono-, di-, and tri-oleates, mono-palmitates and mono-myristates may be used.
ZDDP is combined with other compositions that provide antiwear properties. U.S. Pat. No. 5,034,141 discloses that a combination of a thiodixanthogen compound (octylthiodixanthogen, for example) and a metal thiophosphate (ZDDP, for example) can improve antiwear properties. U.S. Pat. No. 5,034,142 discloses that use of a metal alkyoxyalkylxanthate (nickel ethoxyethylxanthate, for example) and a dixanthogen (diethoxyethyl dixanthogen, for example) in combination with ZDDP improves antiwear properties. Each of the aforementioned patents is incorporated herein by reference in its entirety.
Preferred antiwear additives include phosphorus and sulfur compounds such as zinc dithiophosphates and/or sulfur, nitrogen, boron, molybdenum phosphorodithioates, molybdenum dithiocarbamates and various organo-molybdenum derivatives including heterocyclics, for example dimercaptothiadiazoles, mercaptobenzothiadiazoles, triazines, and the like, alicyclics, amines, alcohols, esters, diols, triols, fatty amides and the like can also be used. Such additives may be used in an amount of about 0.01 to 6 wt %, preferably about 0.01 to 4 wt %. ZDDP-like compounds provide limited hydroperoxide decomposition capability, significantly below that exhibited by compounds disclosed and claimed in this patent and can therefore be eliminated from the formulation or, if retained, kept at a minimal concentration to facilitate production of low SAP (sulfur, phosphorous and ash) formulations.
In addition, there is a growing demand for improved energy efficiency in vehicles. The use of low viscosity engine lubricants may be used in improving fuel economy in internal combustion engines by reducing viscous drag losses. However, under high load and/or low speed conditions, the thinner lubricant films result in more direct contact between surfaces causing high surface friction and wear. Hence, there is a need for new and improved antiwear additives for engine oils that can retain wear performance with low viscosity engine oils intended to improve fuel efficiency.
Corrosion Inhibitor Additives:
Corrosion inhibitors are used to reduce the degradation of metallic parts that are in contact with the lubricating oil compositions. Suitable corrosion inhibitors include thiadiazoles. See, for example, U.S. Pat. Nos. 2,719,125; 2,719,126; and 3,087,932. Such additives may be used in an amount of about 0.01 to 5 wt %, preferably about 0.01 to 1.5 wt %. There is also a need for improved corrosion inhibitor additives for lubricating oil compositions that further reduce degradation of metallic parts during use.